U.S. patent number 5,279,305 [Application Number 07/926,230] was granted by the patent office on 1994-01-18 for electroencephalograph incorporating at least one wireless link.
This patent grant is currently assigned to Pedifutures, Inc.. Invention is credited to David V. Blankenship, Brian T. Pepper, Andrew W. Zimmerman.
United States Patent |
5,279,305 |
Zimmerman , et al. |
January 18, 1994 |
Electroencephalograph incorporating at least one wireless link
Abstract
An improved EEG system (10) for telemetrically transmitting
brain activity data from a portable transmitter to a processing
console. The improved EEG system (10) includes a lightweight
transmitter (12) which amplifies and digitizes the EEG signals from
a set of electrodes (16) and transmits the digital signals along
with a checksum to a receiver (14). The transmitter (12) may be
carried by the subject under observation. The transmitter (12) of
the preferred embodiment includes at least four circuit boards
including a selectively interchangeable montage board (18), an
amplifier board (24), a processor board (34), and a transmitter
board (54). A signal is transmitted toward the receiver (14) and
delivered to a conventional computer-controlled broadcast
television tuner (80). The selected receiver (14) outputs data
which is in an acceptable form for connection to standard
microprocessor peripherals. The incoming data is processed and
inspected to verify the validity thereof with any invalid data
being marked as invalid. All data is then continuously and
simultaneously displayed and recorded, with any invalid data being
easily recognized as such and therefore disregarded.
Inventors: |
Zimmerman; Andrew W. (Knox,
TN), Pepper; Brian T. (Knox, TN), Blankenship; David
V. (Knox, TN) |
Assignee: |
Pedifutures, Inc. (Oak Ridge,
TN)
|
Family
ID: |
25452922 |
Appl.
No.: |
07/926,230 |
Filed: |
August 6, 1992 |
Current U.S.
Class: |
600/544;
128/903 |
Current CPC
Class: |
A61B
5/369 (20210101); A61B 5/0006 (20130101); Y10S
128/903 (20130101) |
Current International
Class: |
A61B
5/00 (20060101); A61B 5/0476 (20060101); A61B
005/0476 () |
Field of
Search: |
;128/639,640,644,731,732,903,904 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kamm; William E.
Assistant Examiner: Manuel; George
Attorney, Agent or Firm: Pitts & Brittian
Claims
Having thus described the aforementioned invention.
1. An improved electroencephalograph system for telemetrically
transmitting data to a selected receiver, said data being detected
by a plurality of sensors selectively attached to a subject in a
selected arrangement, said improved electroencephalograph system
comprising:
a first receiving means for receiving said data detected by said
plurality of sensors, said data including signals indicating brain
activity of said subject and used for selective monitoring of said
subject;
processing means for converting said data into a selected digital
code suitable for telemetric transmission, said selected digital
code being Manchester code;
transmitting means for transmitting said coded data to said
selected receiver at a selected frequency;
second receiving means carried by said selected receiver to receive
said coded data transmitted by said transmitting means;
decoding means in communication with said second receiving means
for decoding said coded data transmitted by said transmitting
means; and
user interface means for performing selected functions using said
decoded data for continuous display/recording thereof.
2. The improved electroencephalograph system of claim 1 further
comprising an amplification means for amplifying said data detected
by said plurality of sensors and sending said amplified signals to
said processing means.
3. The improved electroencephalograph system of claim 1 further
comprising a data testing means for testing an integrity of said
decoded data and further for indicating any of said data wherein
said integrity has been damaged.
4. The improved electroencephalograph system of claim 3 wherein
said data testing means includes a generator means, a comparator
means and an identification means, said generator means for
generating a selected indicator for simultaneous processing and
transmission with said data detected by said plurality of sensors,
said comparator means for comparing said selected indicator
generated by said generator means with said selected indicator
received after being coded by said processing means, transmitted by
said transmitting means, and decoded by said decoding means, said
identification means for identifying said decoded data transmitted
simultaneously with said selected indicator when said decoded
selected indicator varies from said selected indicator generated by
said generator means.
5. The improved electroencephalograph system of claim 1 wherein
said first receiving means includes a selected montage board for
attaching said plurality of sensors in said selected
arrangement.
6. The improved electroencephalograph system of claim 5 wherein
said montage board is selectively removable for replacement by
another said selected montage board defining another said selected
arrangement.
7. The improved electroencephalograph system of claim 1 further
comprising a frequency selecting means for selecting said selected
frequency.
8. The improved electroencephalograph system of claim 1 wherein
said user interface means is further used to perform at least a
portion of said selected functions using said decoded data which
has been previously recorded by said user interface means for
continuous display thereof.
9. An improved electroencephalograph system for telemetrically
transmitting data to a selected receiver, said data being detected
by a plurality of sensors selectively attached to a subject in a
selected arrangement, said improved electroencephalograph system
comprising:
a first receiving means for receiving said data detected by said
plurality of sensors, said first receiving means including a
selected montage board for attaching said plurality of sensors in
said selected arrangement, said data including signals indicating
brain activity of said subject and used for selective monitoring of
said subject;
amplification means for amplifying said data;
processing means for converting said amplified data into a selected
digital code suitable for telemetric transmission, said processing
means including a generator means for generating a selected
indicator for simultaneous processing and transmission with said
amplified data, said selected digital code being Manchester
code;
transmitting means for transmitting said coded data and said coded
indicator to said selected receiver at a selected frequency;
second receiving means carried by said selected receiver to receive
said coded data and said coded indicator transmitted by said
transmitting means;
decoding means in communication with said second receiving means
for decoding said coded data and said coded indicator transmitted
by said transmitting means;
comparator means for comparing said selected indicator generated by
said generator means with said decoded indicator received after
being decoded by said decoding means;
identification means for identifying said decoded data transmitted
simultaneously with said selected indicator when said decoded
indicator varies from said selected indicator generated by said
generator means; and
user interface means for performing selected functions using said
decoded data for continuous display/recording thereof and further
to perform at least a portion of said selected functions using said
decoded data which has been previously recorded by said user
interface means for continuous display thereof.
10. The improved electroencephalograph system of claim 9 wherein
said montage board is selectively removable for replacement by
another said selected montage board defining another said selected
arrangement.
11. The improved electroencephalograph system of claim 9 further
comprising a frequency selecting means for selecting said selected
frequency.
12. A method of telemetrically transmitting signals sensed using an
improved electroencephalograph system for transmitting data to a
selected receiver, said method of telemetrically transmitting
signals comprising the steps of:
sensing said signals by a plurality of sensors selectively attached
to a subject in a selected arrangement;
sending said signals to a selected processing means;
amplifying said signals within said processing means;
generating a selected indicator for simultaneous processing with
said amplified signals;
converting said amplified signals and said selected indicator into
a selected digital code suitable for telemetric transmission, said
selected digital code being Manchester code;
transmitting said coded signals and said coded indicator at a
selected frequency;
receiving said coded signals and said coded indicator by a selected
receiving means;
decoding said coded signals and said coded indicator;
comparing said selected indicator with said decoded indicator;
identifying said decoded signals transmitted simultaneously with
said decoded indicator when said decoded indicator varies from said
selected indicator generated by said generator means; and
selectively and continuously displaying and recording said decoded
signals.
13. The method of telemetrically transmitting signals of claim 12
further comprising the step of selecting said arrangement for said
attachment of said plurality of sensors to said subject prior to
said step of sensing said signals by said plurality of sensors
selectively attached to said subject in said selected
arrangement.
14. The method of telemetrically transmitting signals of claim 12
further comprising the step of selecting said frequency prior to
said step of transmitting said coded signals and said coded
indicator at said selected frequency.
Description
TECHNICAL FIELD
This invention relates to the field of monitoring brain activity.
More specifically, this invention relates to an
electroencephalograph (or EEG) device for monitoring and recording
brain activity wherein wireless links are incorporated for
communication between activity-detecting electrodes and a
processing device.
BACKGROUND ART
In the field of monitoring brain activity the use of
electroencephalograph devices (EEG's) is well known. EEG's are used
to measure and record small electrical signals which occur on the
surface of the scalp as a result of brain activity. Typically, an
EEG system includes a plurality of electrodes attached at selected
positions on the subject's scalp, a corresponding number of lead
wires, and a processing console. Typically, each electrode is
connected to the processing console via a separate lead wire. The
processing console is provided for signal selection, amplification,
and conditioning. Also included in EEG systems are means for
measuring electrode impedance, calibrating equipment, and observing
and permanently recording data processed by the processing
console.
It is well known that the processing console and the observation
and recording equipment are often incorporated within a single
unit. The single unit, however, is too large to be easily
transportable by the subject under observation. Further, because
long wires between the electrodes and the processing console are
impractical, the subject must remain relatively stationary when
using most available EEG systems.
Some EEG systems have been developed to overcome the problem of the
subject having to remain still during observation. These devices
include portable recorders which may be carried by the subject
under observation. These systems do not, however, include means for
contemporaneous observation of the record. It is well known that
such observation is often desired.
One method for making EEG measurements and contemporaneous
observations more practical is to replace the wire links between
the electrodes and the processing console with wireless links.
Thus, situations such as those described above--i.e., when long
wires might encumber other simultaneous attention needed by the
subject or when the mobility of the subject might be
impaired--would be at least partially resolved.
Other devices have been produced to monitor, process and record
data received from the vital organs of a body. Typical of the art
are those described in the following U.S. Patents:
______________________________________ U.S. Pat. No. Inventor Issue
Date ______________________________________ 3,253,588 R. F.
Vuilleumier, et al. May 31, 1966 3,859,988 C. C. Lencioni, Jr. Jan.
14, 1975 3,943,918 R. A. Lewis Mar. 16, 1976 4,089,329 L. A.
Couvillon, Jr., et al. May 16, 1978 4,186,749 T. B. Fryer Feb. 5,
1980 4,245,645 P. M. Arseneault, et al Jan. 20, 1981 4,279,258 E.
R. John Jul. 21, 1981 4,409,987 R. A. McIntyre Oct. 18, 1983
4,471,786 H. Inagaki, et al. Sep. 18, 1984 4,495,950 D. E.
Schneider Jan. 29, 1985 ______________________________________
Of these patents, the U.S. Pat. Nos. 3,253,588 ('588); 3,943,918
('918); 4,089,329 ('329); 4,186,749 ('749); and 4,471,786 ('786)
patents disclose devices which incorporate telemetric transmittal
of sensed data to a selected processing center. Each discloses a
device using transmission over radio frequencies (r-f) using
amplitude modulation (AM) or frequency modulation (FM) methods
similar to those used for broadcast radio. The transmitted signals
are thus subject to the same interference and distortion as
broadcast radio signals.
It is well known that FM transmissions are more reliable than AM
transmissions. However, it is also known that FM signals are
subject to distortion and interference from signals broadcast from
other stations. Though in the field of radio broadcasting these
disturbances are mostly annoyances to signal receptors, in the
field of EEG monitoring such disturbances will provide erroneous
data concerning the brain activity of the subject. In this context,
distortion and interference is detrimental to accurate analysis and
is therefore undesirable.
Therefore, it is an object of this invention to provide a means for
transmitting signals detected by electrodes placed on a subject's
body to a signal processor using telemetric methods.
It is also an object of the present invention to substantially
reduce the distortion and interference typically present in
standard transmission of radio frequency signals.
Another object of the present invention is to provide an
electroencephalographic monitoring and recording device wherein
digital data communications is incorporated to provide accurate
transmission of detected brain activity signals.
Still another object of the present invention is to provide a
lightweight transmitter for amplifying and digitizing EEG signals
from the electrodes.
Yet another object of the present invention is to provide a means
whereby the data transmitted may be checked and verified to insure
that data received by a receiving device is valid, and further that
any invalid data received is ignored.
DISCLOSURE OF THE INVENTION
Other objects and advantages will be accomplished by the present
invention which serves to detect brain activity in a subject and
transmit the detected signals telemetrically to a processing
center. The telemetric method used incorporates digital data
communications in order to provide accurate transmittal of the
detected signals. The improved EEG system of the present invention
includes a lightweight transmitter which amplifies and digitizes
the EEG signals from a set of electrodes and transmits the digital
signals along with a checksum to a receiver. The checksum allows
the receiver to verify the validity of the received data and to
denote any data which has been distorted or subjected to
interference between the transmitter and receiver.
The transmitter is designed to be carried by the subject under
observation. A plurality of electrodes are electrically connected
to the transmitter and are attached to the subject in a
conventional fashion. The transmitter of the illustrated embodiment
includes four circuit boards upon which the electronic circuitry is
configured. These circuit boards include a selectively
interchangeable montage board, an amplifier board, a processor
board, and a transmitter board.
The montage board is provided for selectively configuring the
connections between the electrodes and the remainder of the EEG
system. The montage board may be selectively interchanged to change
the configuration of the electrode connections.
The amplifier board is provided for amplifying the small signals
detected by the electrodes. In the preferred embodiment, the
amplifier board includes a plurality of signal amplifiers. The
connection of the amplifiers to the electrodes is determined by the
selected montage board installed with a selected pair of electrodes
being connected to the respected inputs of a signal amplifier.
The processor board digitizes the amplified signals and converts
them to a form suitable for transmission. The processor board
includes a plurality of inputs for receiving the individual outputs
of the signal amplifiers. In the preferred embodiment, the
processor board is programmed to control multiplexing, conversion
of the selected amplifier outputs within the A-D converter to
binary-coded digital data, calculation of a binary checksum number,
conversion of the binary-coded digital numbers and checksum number
to a selected code suitable for transmission of digital data, and
generation of a precisely-timed serial data stream from the numbers
coded in the selected code.
The transmitter board further converts the signals into radio
frequency (r-f) signals for transmission. The serial data stream
generated by the microprocessor is delivered through an amplifier
to an oscillator carried by the transmitter board. The amplifier is
also used to select the rate of frequency change of the oscillator
in order to conform to regulations imposed by the Federal
Communications Commission (FCC) and further to meet other selected
output requirements as well. The oscillator is also controlled by a
phase-locked-loop system which will allow for the control of the
center frequency of the oscillator.
The output of the oscillator is connected to an antenna via a trap,
the trap serving to filter out unwanted harmonic frequencies in
order to avoid interference with other transmissions.
The signal from the transmitter is received by the receiver antenna
and delivered to a conventional computer-controlled broadcast
television tuner. The output of the TV tuner is connected to a
selected receiver. The combination of the TV tuner and the selected
receiver form a double-superheterodyne receiver capable of
rejecting out-of-band image signals.
The selected receiver outputs a reconstituted serial data stream
substantially identical to the selectively-coded serial data stream
generated by a microcontroller incorporated by the transmitter
processor board. The data stream is sent to a decoder for
converting the coded data stream to a synchronous nonreturn-to-zero
code (NRZ) serial data stream. The synchronous NRZ serial data is
an acceptable form for connection to standard microprocessor
peripherals.
The incoming data is processed by a selected microprocessor which
inspects the checksum generated by the transmitter microcontroller.
For any checksum detected to be incorrect, the associated data is
marked such that observation of the distorted data will reflect the
distortion and can be easily disregarded. All data, whether valid
or invalid, is sent to a second communications interface configured
to perform as a standard asynchronous serial port which may be
connected to any standard computer serial port. The data may then
be displayed and recorded as desired.
BRIEF DESCRIPTION OF THE DRAWINGS
The above mentioned features of the invention will become more
clearly understood from the following detailed description of the
invention read together with the drawings in which:
FIG. 1 is a block diagram illustrating the functions of a
transmitter and a receiver constructed in accordance with several
features of the present invention;
FIG. 2 is a plan view of a montage board incorporated within a
transmitter of FIG. 1;
FIG. 2A is a plan view of the montage board of FIG. 2 showing a
preferred etching schematic on a first side thereof;
FIG. 2B is a plan view of the montage board of FIG. 2 showing a
preferred etching schematic on a second side thereof;
FIG. 3 is a schematic diagram of the circuitry of the amplifier
board incorporated in the transmitter of FIG. 1;
FIG. 4 is a schematic diagram of the circuitry of the processing
board incorporated in the transmitter of FIG. 1;
FIG. 5 is a schematic diagram of the circuitry of a preferred
microcontroller incorporated in the processing board of FIG. 4;
FIG. 6 is a schematic diagram of the circuitry of the transmitter
board incorporated in the transmitter of FIG. 1;
FIG. 7 is a schematic diagram of the circuitry of the receiver
board incorporated in the receiver of FIG. 1; and
FIG. 8 is a schematic diagram of the circuitry of the input/output
board incorporated in the receiver of FIG. 1.
BEST MODE FOR CARRYING OUT THE INVENTION
An electroencephalograph (EEG) system incorporating various
features of the present invention is illustrated generally at 10 in
the figures. The EEG system 10 is designed for adapting digital
data communications techniques to the requirements of EEG
recording. In the preferred embodiment the EEG system 10 includes a
lightweight transmitter 12 which amplifies and digitizes the EEG
signals from a plurality of electrodes 16 and transmits the digital
signals along with a checksum to a selected receiver 14. The
checksum allows the receiver 14 to verify the validity of the
received data and to denote any data which has been distorted or
subjected to interference between the transmitter 12 and receiver
14. It is envisioned, though not shown, that the lightweight
transmitter 12 may also be used to transmitted EEG signals over
standard telephone wire to a processing station at a remote
location where telemetric signals may not be accurately
transmitted.
The transmitter 12 is designed to be carried by the subject under
observation. A plurality of electrodes 16 is electrically connected
to the transmitter 12 and is attached to the subject in a
conventional fashion. The transmitter 12 of the illustrated
embodiment includes four circuit boards upon which the electronic
circuitry is configured. It is envisioned that the transmitter 12
may be constructed on any selected number of circuit boards. FIG. 1
illustrates the relationship between the four circuit boards.
A montage board 18 is provided for selectively configuring the
connections between the electrodes 16 and the remainder of the EEG
system 10. The operator of the EEG system 10 may alter the
configuration of the electrode connections by replacing the montage
board 18 with another defining the selected configuration. The
electrodes 16 are connected to the montage board 18 in a
conventional fashion as with a ribbon-type cable and connector. A
typical montage board 18 is illustrated in FIGS. 2, 2A, and 2B.
An amplifier board 24 is provided for amplifying the small signals
detected by the electrodes 18. In the preferred embodiment, the
amplifier board 24 includes at least eight signal amplifiers
illustrated generally at 26. The connection of the signal
amplifiers 26 to the electrodes 16 is determined by the selected
montage board 18 installed. A selected pair of electrodes 16 is
connected to the respective inputs 28,30 of a signal amplifier
26.
Each of the signal amplifiers 26 uses three operational amplifier
(op-amp) elements as opposed to the typical minimum of four. As
shown in FIG. 3, six op-amps OA1-6 are included on the preferred
amplifier board 24. Each op-amp OA1-6 shown includes four elements,
or pins, which are designated for use in the signal amplifiers 26.
These pins are designated as P3, P5, P7, and P12 for each op-amp
OA1-6. The pins P3 and P12 of each op-amp OA1-6 are shown as being
used as input pins while pin P7 of each op-amp OA1-6 is shown as
being an output pin for the respective input pins P3 and P12. Thus,
the respective sets of pins P3, P7, and P12 each define a single
signal amplifier 26. The inputs OA1-P3 and OA1-P12, as illustrated,
are connected in series with a selected capacitor C1 therebetween.
The designation OA1-P3 denotes pin P3 of op-amp OA1, etc. The
respective pairs of input pins from the op-amps OA2 through OA6 as
described are configured in similar fashion with capacitors C2
through C6, respectively.
The pins P5 of the op-amps OA1 and OA2 are shown as inputs and pin
P5 of the op-amp OA3 is shown as the output of a seventh signal
amplifier 26. The pins P5 of the op-amps OA4, OA5, and OA6 are
arranged in similar fashion to define an eighth signal amplifier
26. Inputs OA1-P5 and OA2-P5 are connected by a capacitor C7 while
inputs OA4-P5 and OA5-P5 are connected by a capacitor C8.
It will be seen that one fewer op-amp is required for every four
signal amplifiers 26 desired as described in the present invention.
By utilizing fewer op-amps and other components, the requirements
of high input-resistance in a differential input configuration and
high gain are achieved These requirements are similar to those of a
conventional EEG system.
A processor board 34 digitizes the amplified signals and converts
them to a form suitable for transmission. The processor board 34
includes a plurality of inputs 36 for receiving the individual
outputs 32 of the amplifiers 26. A microcontroller 38 is utilized
in the preferred embodiment for combining the functions of an
analog multiplexer and analog to digital (A-D) converter 40, a
microprocessor 42, data memory 44, and non-volatile program memory
46. FIG. 5 illustrates, in block-diagram form, the functions of a
preferred microcontroller 38. One microcontroller 38 which may be
used is the MC68HC811E2 high-density CMOS (HCMOS) Microcontroller
Unit (MCU) manufactured by Motorola.
The selected microcontroller 38 may be programmed to perform
selected functions. In the preferred embodiment, the
microcontroller 38 is programmed to control multiplexing,
conversion of the selected amplifier outputs 32 within the A-D
converter 40 to binary-coded digital data, calculation of a binary
checksum number, conversion of the binary-coded digital numbers and
checksum number to a selected code suitable for transmission of
digital data, and generation of a precisely-timed serial data
stream from the numbers coded in the selected code. One selected
code which is preferred is known as the Manchester code, which will
be discussed in more detail below.
The A-D converter 40 incorporated within the microcontroller 38 is
capable of performing the first two processes. Namely, the A-D
converter 40 performs the sequential selection of the signal
amplifier outputs 32 for connection thereto, or multiplexing, and
the conversion of the selected signal amplifier outputs 32 to
binary-coded digital data. The digital data is temporarily stored
in memory, such as in random access memory indicated at 44.
The microprocessor 42 performs the latter three functions.
Specifically, the microprocessor 42 calculates a binary checksum
number, converts the binary-coded digital numbers and checksum
number to a selected code suitable for transmission of digital
data, and generates a precisely-timed serial data stream from the
numbers coded in the selected code. The A-D converter 40 is also
controlled by the microprocessor 42. A voltage regulator 48, a
watchdog 50, and the components of a crystal oscillator 52 are
shown as typical peripherals to the microprocessor 42.
A transmitter board 54 further converts the signals into radio
frequency (r-f) signals for transmission. The serial data stream
generated by the microprocessor 42 is delivered through an
amplifier 56 to an oscillator 58 carried by the transmitter board
54. The amplifier 56 is also used to select the rate of frequency
change of the oscillator 58 in order to conform to regulations
imposed by the Federal Communications Commission (FCC). It will be
noted that the rate of frequency change of the oscillator 58 may be
selectively changed within the imposed regulations to meet other
selected output requirements as well. The modulation of the
oscillator 58 by a digital signal in this manner is typically
denoted as frequency shift keying, or FSK.
The oscillator 58 of the illustrated embodiment is also controlled
by a phase-locked-loop system 60 comprising at least two selected
components 62,64. In the preferred embodiment, components 62,64
such as the MC145157, which is a serial input phase-locked-loop
frequency synthesizer, and MC12023, which is a frequency divider,
manufactured by Motorola may be used. The phase-locked-loop system
60 allows the center frequency of the oscillator 58 to be precisely
controlled to conform to regulations imposed by the FCC and to be
selectable by the microcontroller 38 incorporated in the processor
board described above. The component 62 may select from at least
two frequencies for the center frequency of the oscillator 58. The
frequency is selected by the component 62 by monitoring a
user-selectable input 70 carried by the montage board 18.
In the preferred embodiment, the response time of the control
exerted on the oscillator 58 by the phase-locked-loop system 60 is
longer than the response time of the control exerted by the FSK
modulation input. The longer response time is desirable to prevent
the negation of the effect of the FSK modulation control.
The output of the oscillator 58 is connected to an antenna 66 via a
trap 68. The trap 68 serves to filter out unwanted harmonic
frequencies in order to avoid interference with other
transmissions.
The Manchester code referred to above has as its principal feature
a substantially equal time spent in the two possible modulating
states. Therefore, there is substantially little danger of a
repeated coded sequence causing a bias to one state or the other
when averaged over a period approaching the response time of the
phase-locked-loop system 60. The use of binary code has been found
to allow such biasing, which causes a shift of the center of the
frequency of the oscillator 58. When such a frequency shift occurs,
the performance of the overall system 10 may be impaired and FCC
regulations may be contravened.
Referring again to FIG. 1, the signal from the transmitter 12 is
received by the receiver antenna 78 and delivered to a conventional
computer-controlled broadcast television tuner 80. The output of
the TV tuner 80 is connected to an FSK receiver 82 which includes
at least one FSK receiver chip 84. One preferred FSK receiver chip
84 is the MC3356 manufactured by Motorola. The combination of the
TV tuner 80 and the FSK receiver 82 form a double-superheterodyne
receiver 86 capable of rejecting out-of-band image signals.
The FSK receiver 82 outputs a reconstituted serial data stream
substantially identical to the selectively-coded serial data stream
generated by the microcontroller 38 incorporated by the transmitter
processor board 34. As described above, this serial data stream may
be Manchester-coded in a preferred embodiment. The data stream is
sent to a decoder 88 for converting the coded data stream to a
synchronous nonreturn-to-zero code (NRZ) serial data stream. The
synchronous NRZ serial data is an acceptable form for connection to
a standard microprocessor peripheral 90. Typical of the standard
microprocessor peripherals is the Intel 8251A communications
interface.
The incoming data is processed by a selected microprocessor 92 such
as the Zilog Z80. The microprocessor 92 inspects the checksum
generated by the transmitter microcontroller 38. In the preferred
embodiment, if any checksum is detected to be incorrect, the
microprocessor 92 changes each number in the associated data set to
zero as an indication to the system operator that the data is
invalid. It will be understood that other forms of indication may
be incorporated as well.
The data, whether found to be valid or invalid, is sent by the
microprocessor 92 to a second communications interface 94. The
second communications interface 94 of the preferred embodiment is
configured to perform as a standard asynchronous serial port which
may be connected to any standard computer serial port. The data may
then be displayed and recorded as desired.
A selected software program has been developed to perform the
selected functions of the improved EEG system 10. The software
includes two segments, the first being an interrupt service
routine, and the second being the main program.
The interrupt service program is normally initiated when the
computer is booted, but may be initiated at any time prior to the
initiation of the main program. The interrupt service program is
executed one time, during which are performed initialization tasks
such as reserving a selected amount of memory at a selected
address. The interrupt service routine is a terminate and stay
program which receives the decoded data from the FSK receiver 82
via a selected link. One selected link is a 19,200 baud RS-232
link. When a byte of data is received, the computer is interrupted
and the data placed into a circular buffer in memory. The circular
buffer of one embodiment is defined with a capacity of 16,000 (16
K) bytes of memory. This memory is located at a selected address in
memory for accessibility by the main program.
The main program may be in the format of a Disk Operating System
(DOS) program. The main program functions to retrieve data from the
interrupt service routine circular buffer and format, display, and
log the data to a series of disk files. From these disk files,
previously recorded monitoring sessions may be reviewed, displayed,
and/or printed at any selected time.
After initialization of the main program, the user will have the
option to record a new session or to review a previously recorded
session. If a new session is selected, the user will be requested
to provide information about the subject. This information may
include identification information regarding the patient and any
comments an observer may wish to make. After response has been made
to any initialization questions, the recording session will
begin.
While the program is in the recording mode, each of the EEG signals
is displayed as a single horizontal line of data. In the preferred
embodiment, eight channels will produce eight horizontal lines of
data to represent eight signals. The main program is designed such
that each line of data scrolls from right to left on the display
terminal such that the display contains the previous eight to ten
seconds of data for each of the EEG signals received. Of course,
the time of display for a single point of data is dependent on at
least the rate of scroll and the dimensions of the display
terminal. During the display of the data, recordation of the data
is simultaneously being accomplished for later analysis, review
and/or printing.
During the recordation of the monitoring session, several selected
functions may be available to the user. Of these include: the
selective viewing of vertical lines on the screen to indicate time
increments such as 1-second intervals; the ability to freeze the
display; the ability to change the vertical scale or sensitivity of
the display; and the ability to make notations in the data file to
emulate a clinician making notes on a paper polygraph. When
selectively changing the appearance of the data on the
screen--i.e., changing the scale, freezing the screen, etc.--the
data being stored is unaltered. Therefore, a later review of the
session will not reveal that these functions were utilized in the
original session. When no data is being received by the software,
the display terminal will cease to scroll.
When reviewing a previously recorded session, the user may scroll
through the data in either forward or backward directions, vary the
vertical scale as before, and add or remove the time increment
indicators. Additionally, the user may print the screen being
viewed, or he may print the entire data file as a continuous "tape"
on a standard continuous form printer. Due to the digital
transmission techniques as described above, the recordation of the
data is ensured to be accurate such that the subsequent review of
the data will be substantially identical to the viewing of the
original session and no degradation of the data will occur.
From the foregoing description, it will be recognized by those
skilled in the art that an EEG system 10 offering advantages over
the prior art has been provided. Specifically, the EEG system 10
provides a means for adapting digital data communications
techniques to the requirements of EEG recording. The EEG system 10
of the preferred embodiment includes a means for transmitting brain
signals to a processing console for observation and recording. The
data transmitted is selectively coded for accurate transmission.
Means for verifying the accuracy of the transmitted data are
provided, thereby allowing for the disposal of data which is
distorted during transmission. Thus substantially all data observed
and recorded is verified as accurate.
While a preferred embodiment has been shown and described, it will
be understood that it is not intended to limit the disclosure, but
rather it is intended to cover all modifications and alternate
methods falling within the spirit and the scope of the invention as
defined in the appended claims.
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